The demand for high capacity rechargeable batteries is extensive. Many applications, such as aerospace, medical devices, portable electronics, automotive and many others, demand high gravimetric and or volumetric capacity batteries. Development of the lithium ion technology has provided some advances in this area, but higher capacities are still very desirable. Lithium ion cells generally use anodes containing graphite powder that has theoretical capacity of only about 372 mAh/g.
Silicon is an attractive insertion material for lithium and other electrochemically active ions. A theoretical capacity of silicon in lithium ion cell has been estimated at about 4200 mAh/g. Yet use of silicon and many other high capacity materials for battery applications has been constrained by substantial changes in volume (swelling) of these materials during insertion of active ions. For example, silicon swells as much as 400% during lithiation. Volume changes of this magnitude cause substantial stresses in silicon structures in the negative electrodes resulting in pulverization of the structures, loss of electrical connections within the electrode, and capacity fading of the battery. Further, many high capacity materials, such as silicon, have poor electrical conductivity, and often require special design features or conductive additives that may negatively impact battery capacity. Overall, there is a need for improved application of high capacity active materials in battery electrodes that minimize the drawbacks described above.